Incomplete Dominance Neither allele is dominant over the other Heterozygous offspring have a phenotype that is somewhere between the two. Red + White = ___________

Incomplete Dominance RR x WW yields heterozygous offspring Homozygous red parent: RR crossed with Homozygous white parent: WW RR x WW yields heterozygous offspring RW that are pink

Incomplete Dominance

X Codominance Both alleles contribute to the phenotype Heterozygous offspring express both alleles X

Codominance: A black chicken crossed with a white chicken results in a speckled chicken How is this type of inheritance different from incomplete dominance?

Multiple Alleles > 2 possible alleles exist in a population Coat color in rabbits: at least 4 different alleles C = full color (dominant other alleles) c (ch) = chinchilla c (h) = himalayan c = albino (recessive other alleles)

Full Color Rabbit (C)

partial defect in pigmentation: c (ch) Chinchilla Rabbit partial defect in pigmentation: c (ch)

Himalayan Rabbit Color in only certain parts of body: c (h)

Albino Rabbit (c)

Polygenic Traits Traits that are produced by the interaction of more than one different genes Example: coat color in Labrador retrievers is a result of interaction of 2 different genes.

Polygenic Inheritance 2 or more genes work together to create a single phenotype Ex: Eye color, skin color

Polygenic Inheritance Example: comb shape in chickens is a result of interaction between 2 different genes.

Epistasis When one gene product affects the expression of another gene. B, b = fur color alleles bb = brown fur Fur color only expressed if C gene is also present